1. Technical Field
The present disclosure relates to a hydrogen generating apparatus, a fuel cell system, and methods of operating them.
2. Description of the Related Art
Because infrastructures to supply hydrogen-containing gas are not yet built up on the widespread basis, equipment using the hydrogen-containing gas as fuel, represented by a fuel cell system, usually includes a hydrogen generating apparatus equipped with a reformer for generating the hydrogen-containing gas from a raw material, e.g., natural gas or LPG, which is prevailed as general raw-material infrastructure gas.
The raw material may contain a sulfur compound as an odorant. Because the sulfur compound is particularly a poisoning material for a reformation catalysis, it has to be removed from the raw material by any method. There is provided a hydrogen generating apparatus that employs a method of recycling part of the generated hydrogen-containing gas and removing the sulfur compound through hydrodesulfurization.
International Publication No. 2011/077752 discloses a hydrogen generating apparatus including a first desulfurizer that adsorptively removes a sulfur compound in a raw material gas supplied to a reformer, a second desulfurizer that performs hydrodesulfurization of the sulfur compound in the raw material gas supplied to the reformer, a first passage through which the raw material gas is supplied to the reformer via the first desulfurizer, a second passage through which the raw material gas is supplied to the reformer via the second desulfurizer, but not via the first desulfurizer, a switching device that switches over the first passage and the second passage, and a controller, wherein the controller controls the switching device such that the raw material gas flows through the first passage during at least one of a pressure supplementing operation for replenishing the raw material gas to compensate for an internal pressure drop after an operation of generating the hydrogen-containing gas and a raw-material gas purging operation of purging the inside of the hydrogen generating apparatus with the raw material gas.